[escher] make an independent class alternate empty view to handle

empty store and add a delegate to the header view controller class

Change-Id: I7c4e8342876e9273270772d4bad0db9424276a98

escher/src/header_view_delegate.cpp

@@ -0,0 +1,20 @@
+#include <escher/header_view_delegate.h>
+#include <assert.h>
+
+HeaderViewDelegate::HeaderViewDelegate(HeaderViewController * headerViewController) :
+  m_headerViewController(headerViewController)
+{
+}
+
+int HeaderViewDelegate::numberOfButtons() const {
+  return 0;
+}
+
+Button * HeaderViewDelegate::buttonAtIndex(int index) {
+  assert(false);
+  return nullptr;
+}
+
+HeaderViewController * HeaderViewDelegate::headerViewController() {
+  return m_headerViewController;
+}